Discoloration on waterblock

[MysticalOrca]

Howdy, I just looked at my cpu waterblock, the phobya UC-2 LT, after leaving it sitting in my room for a couple of days and something happened to it. I took these two pictures because I really don't know how to describe it. I was hoping someone could tell me if this is normal and if I should be concerned putting it into my system. It seemed like the surface was still very smooth but I just want to be sure. Thanks for any help

 

[Nenu]

Looks like residue from a plastic covering has reacted with the surface, or something else it came in contact with.
Use a copper polish to remove it.
I keep duraglit around for keeping things clean.

It probably wont affect temps if you cant feel anything on the surface.

 

[sok0]

Would definitely not use copper polish, that would leave residue. Lemon juice, ketchup, or vinegar would take that off or could some high grit sandpaper.